The invention of the present application involves isokinetic exercise and monitoring machines. Isokinetic exercising is a type of dynamic, as opposed to static, exercise technique. Static exercising is also called isometric and dynamic is often termed isotonic. Isotonic techniques include constant resistance, accommodating resistance and variable resistance, where accommodating resistance is synonymous with isokinetic.
Isokinetic, or accommodating resistance, exercise and monitoring machines supply a matching force for any muscular contraction so that a constant velocity is maintained. That is, whether a prescribed submaximal effort or an absolute maximum contraction is made, the exercising muscles are precisely opposed by the isokentic machine so that a constant velocity is maintained throughout the contraction.
Isokinetic machines are very valuable for a variety of purposes. Such machines have been used in preemployment testing to determine employee compatability with particular work tasks, injury evaluation in the worker's compensation context, rehabilitation exercising, general exercising, and general injury evaluation. Isokinetic machines are particularly useful for evaluating injuries because a submaximal effort is indicated by a lack of reproducibility in the torque or strength output over several repetitions.
Several types of force compensated constant velocity, or isokinetic, machines exist. As discussed in U.S. Pat. No. 3,465,592, issued to J. J. Perrine, there are mechanical, hydraulic and electrical machines that provide an isokinetic characteristic. Electric isokinetic machines, machines that include electromechanical dynamometers, are particularly efficacious because of, among other things, the ease of producing an electrical output that is readily displayed and stored by standard electrical and electronic devices.
One type of electromechanical isokinetic machine is represented by a device manufactured by Cybex Co. of Ronkonkoma, N.Y., a division of Lumex, Inc. The Cybex machine includes an electromechanical dynamometer that has a base including an electrical portion and a lever arm that is pivotally mounted to the base. The muscle or muscle group that is being exercised or evaluated is isolated using straps and supports and a moving portion of a limb, for example, is attached to the lever arm of the dynamometer. As the limb is flexed and extended the amount of muscular force produced will vary depending on several factors, including the angular orientation of the moving portion of the limb, the amount of effort exerted, and the extent of the damage to the limb, and the dynamometer supplies a matching force so that the movement of the limb cannot exceed a threshold velocity. This maximum velocity is predetermined by the physical therapist, for example, and is electrically communicated to the dynamometer base that houses the electromechanical mechanism that is responsible for the accommodating resistance characteristic of the dynamometer. The dynamometer has an electrical output that represents the torque or force developed by the exercising limb. This output may be displayed on a strip chart so that strength, power and work may be further evaluated.
There is a great need for isokinetic machines for exercising and evaluating back muscles. For the purposes of the present application, "back" muscles include all of the trunk and limb muscles that contribute to the extension and flexion of the back. The human back is very susceptible to injury and heretofore it has been very difficult to objectively determine the extent and duration of the injury. Also, pre-employment testing for the back muscles is clearly a useful tool.
An isokinetic machine for exercising and testing back muscles has been developed by the Cybex Co. in conjunction with researchers at the University of Wisconsin-LaCrosse. An individual's lower body is strapped to a support frame while his upper body is restrained by a pivotally movable yoke. The lever arm of a Cybex dynamometer is attached to one corner of the restraining yoke. As the individual flexes and extends his back muscles, the yoke, in contact with the individual's upper body, transmits the muscle-generated forces to the dynamometer lever arm and ultimately to the electromechanical dynamometer mechanism.
Although the LaCrosse type of isokinetic back exercise and monitoring machine is generally useful for its intended purposes, it suffers from several shortcomings. First, the placement of the dynamometer's lever arm with respect to the upper body restraint yoke places an undesirable twisting moment on the dynamometer's lever arm. This twisting moment does not contribute to the measured torque or power generated by the exercising individual and tends to cause binding of the lever arm. In fact, such binding tends to absorb a portion of the torque produced by the back muscles of the individual.
Another problem with the prior art isokinetic back exercising machines, including the LaCrosse machine, is that they do not include a simple vertical adjustment to accommodate persons having various heights. Without such a vertical adjustment the upper body restraining yoke cannot properly and comfortably restrain all exercising individuals.
Still another problem with prior art isokinetic machine is the rapid deceleration suffered by the moving part of the limb, for example, when it reaches the end of its stroke as constrained by the machine.
The LaCrosse isokinetic back machine also lacks a simple horizontal adjustment for the lower body restraint to accommodate persons having various sizes and shapes.
Additionally, the previous devices suffer from a lack of ready portability and inadequate dynamometer base stabilization. When the base of the dynamometer is allowed to move, the entire torque produced by the exercising individual is not indicated by the display and recording devices attached to the dynamometer.
The present invention solves many of the aforementioned problems. In particular, a movable member of a dynamometer is attached to the upper body restraint yoke at a central point, thereby eliminating twisting and binding of the dynamometer's lever arm.
The present invention, in one embodiment, also includes a mechanism for vertical adjustment to accommodate persons of various heights. Similarly, horizontal adjustment of the lower body restraint is provided to accommodate persons of varying girths.
One embodiment of the present invention further includes wheels attached to the support frame, stabilization means for firmly connecting the dynamometer base to the support frame of the machine, and a resilient stop to lessen the rapid deceleration discussed above.